Matonis, who oversaw foreign exchange and credit card interchange for Visa in the early 1990s, argues that Bitcoin is not so restrictive. “All banks have the ability to perform lending functions, even with [the] 100% deposit ratios of Bitcoin,” he wrote in an email. Depositors could place one-year or two-year certificates of deposit at a 2% interest rate, and banks could lend those Bitcoins out at 4%, assuming the risk of repayment on behalf of the borrower, he suggested. The number of Bitcoins in circulation would not increase, but banks would still be performing an age-old role: facilitating the provision of credit by acting as intermediaries. A number of start-ups already offer services in the fledgling Bitcoin economy. They range from the more than a dozen exchanges that allow consumers to turn standard currency into Bitcoins and back for a fee to companies like BitIns...